1. Field of the Invention
This invention relates to the field of H.323 multimedia conferencing. In particular, the invention relates to improvements for scaling H.323 systems.
2. Description of the Related Art
The International Telecommunications Union (ITU) has promulgated a number of different standards for telecommunications. The telecommunications standardization sector is referred to as the ITU-T. One of the standards developed by the ITU-T is the H.323 standard for video, or multimedia, communications over packet-switched networks. The H.323 standard uses other ITU-T standards for encoding, transmitting, and decoding the audio, video, data, and control information.
There are four primary types of devices in the H.323 standard: H.323 terminals, H.323 gateways, H.323 multipoint control units (MCUs) and H.323 gatekeepers. The terminals are multimedia terminals such as personal computers coupled to a local area network (LAN). The H.323 gateways allow the interconnection of other systems with an H.323 network. For example, an H.323 gateway could interconnect plain old telephone service (POTS) with an H.323 network. The gateways can also allow separate networks of H.323 devices to be bridged. The H.323 MCU provides support for multiparty conferencing, such as mixing and switching the audio and video signals, and bridging the conferencing setup signals. The H.323 gatekeeper provides registration, admission, and status services including authentication, address query resolution, and other services for H.323 devices.
One application of the H.323 standard is to replace circuit switched services with packet switched services. Plain old telephone service (POTS) is an example of a service provided on a circuit switched network. Each POTS call requires a dedicated circuit from end-to-end throughout the public switched telephone network (PSTN). By placing H.323 gateways and gatekeepers in telephone central office switching systems it is possible to carry a call over a packet switched network from central office to central office. Similarly, the H.323 standard can be used to provide telephone service over cable systems.
One important component of installing H.323 systems to replace circuit switched central office equipment or to provide telephone service over cable systems is supporting billing and other accounting services. To provide these services, the H.323 gatekeeper can be coupled to back-end servers (BESs) that provide authentication, accounting, billing, and other services.
The H.323 gatekeeper is also responsible for managing access to the network and controlling bandwidth usage. In order to accomplish these tasks, the prior art H.323 gatekeeper retains call status information throughout the call. This means that the H.323 gatekeeper includes data about calls in progress. When the call is finished, the H.323 gatekeeper interfaces with the BESs to update the billing and other information.
If the H.323 gatekeeper fails, all of the information about the calls handled by that H.323 gatekeeper are lost. In a central office or cable system installation, that could result in the loss of the accounting and billing data for ten thousand or more calls in progress. Also, replacing a failed H.323 gatekeeper is difficult because the call state information stored on the H.323 gatekeeper would have to be transferred to the replacement H.323 gatekeeper to prevent disruptions.
Another problem of the prior art is that it may be possible to circumvent the H.323 gatekeeper and thus the billing and access control systems. Techniques such as IP spoofing might be used to circumvent the H.323 gatekeeper and place calls without authorization.
If the prior art techniques are used, the H.323 gatekeeper represents a single non-redundant point of failure. Therefore, it is desirable to have a method of improving the reliability of the H.323 gatekeeper. If the prior art techniques are used, the H.323 gatekeeper billing and access control functions can be circumvented. Therefore, it is desirable to have a method of ensuring that the billing and access control functions of the H.323 gatekeeper can not be circumvented.